1. Field of the Invention
The present invention generally relates to a nozzle plate and a nozzle plate manufacturing method, and more particularly to a nozzle plate to be mounted on an ink jet print head and a manufacturing method therefor.
2. Description of the Related Art
Generally, an ink jet print head for printing alphanumeric characters on recording paper by jetting ink has a nozzle plate (a metal plate) on which a plurality of nozzle apertures from which ink is jetted are formed.
The nozzle plate is hydrophilic with respect to the ink when only a nozzle plate is used. Thus, a water-repellant film is formed on the surface of the nozzle plate, in the interest of improving the performance of the print head by improving the flow of the ink when jetted. This water-repellant film affects the ink jet and therefore must be formed in a condition appropriate for jetting ink.
FIG. 1 and FIG. 2 show examples of a conventional nozzle plate manufacturing methods according to the steps by which each is manufactured. The individual manufacturing methods shown in FIG. 1 and FIG. 2 are basically the same, so an explanation will first be given of the basic method for manufacturing a nozzle plate as shown in FIG. 1.
FIG. 1(A) shows a plate body 2 which forms the nozzle plate 1. This plate body 2 is made for example of stainless steel (SUS) and, as the same drawing shows, a nozzle aperture 3 is previously formed on the plate body 2 by a mechanical process or an etching process. This nozzle aperture 3 is composed of a slanted taper portion 4 and a jet aperture portion 5 from which ink is jetted to the outside.
As shown in FIG. 1(B), the plate body 2 so composed is filled with a resist material 6 (the resist material deposition process). At this time, the resist material 6 is loaded from the taper portion 4 of the plate body 2 and the nozzle 3 is filled with the resist material 6.
The process of depositing the resist material deposits the resist material 6 inside the nozzle aperture 3 and, as shown in FIG. 1(C), a water-repellant film 7 is formed on the surface of the plate body 2 (the surface of the side on which the jet aperture portion 5 is formed) (the water-repellant film formation process). This water-repellant film formation process forms the water-repellant film 7 using a method of applying, for example, a composite plating made of a fluororesin material dispersed over a metal such as nickel, or a thin coating of water-repellant resin material.
The material selected as the water-repellant film 7 is such that it forms a good connection with the plate body 2 but a poor connection with the resist material 6. Therefore, the water-repellant film 7 is formed in locations where the resist material 6 is not deposited. That is, an aperture is formed in the water-repellant film 7 (hereinafter referred to as the water-repellant film aperture 8).
Forming the water-repellant film 7 by the water-repellant film formation process described above and then removing the resist material 6 (the resist material removal process) completes the nozzle plate 1 shown in FIG. 1(D) and FIG. 1(E), in which the plate body 2 is coated with the water-repellant film 7. In this completed condition the nozzle aperture 3 and water-repellant film aperture 8 are connected and ink can be jetted therefrom.
The optimal resist material 6 deposition condition is a condition in which the front edge surface of the resist material 6 is flush with the surface of the plate body 2. In this condition, the diameter of the jet aperture portion 5 of the nozzle aperture 3 and the diameter of the water-repellant film aperture 8 would be the same.
However, a problem arises with this conventional method using a resist material 6 in that the amount of resist material 6 deposited inside the nozzle aperture 3 by the resist material deposition process is difficult to control precisely, hence it is difficult to make the front edge surface of the resist material 6 flush with the surface of the plate body 2. If the front edge surface of the resist material 6 is not flush with the surface of the plate body 2, then the diameters of the jet aperture portion 5 of the nozzle aperture 3 and the diameter of the water-repellant film aperture 8 will not be identical and the ink jet will be difficult to control, adversely affecting the quality of the ink jet print.
It is an object of the present invention to provide a nozzle plate and a nozzle plate manufacturing method in which the amount of ink jetted can be accurately controlled, and in which the problems described above are eliminated.
The above-described object of the present invention is achieved by a nozzle plate comprising a plate body on which is formed a plurality of nozzle apertures each having a jet aperture portion from which ink is jetted and a water-repellant film formed on the plate body, wherein the diameter of each of the jet aperture portions formed on the plate body is identical to the diameter of each of a plurality of water-repellant film apertures formed on the water-repellant film so as to connect with the nozzle apertures. The water-repellant film may be formed from a resinous material.
The above-described object of the present invention is also achieved by a manufacturing method for a nozzle plate to be mounted on an ink jet print head, comprising the steps of (a) forming a water-repellant film on the plate body on which a nozzle aperture having a jet aperture portion from which ink is jetted is formed, and (b) forming on the water-repellant film a plurality of water-repellant film apertures each of the same diameter as the jet aperture portion by using the plate body to mask an area surrounding the nozzle aperture and using a removing means to remove such water-repellant film entering and remaining inside the nozzle apertures during formation of the water-repellant film.
The nozzle plate manufacturing method described above may further comprise the step of applying protective tape to a surface opposite the surface on which the plurality of jet aperture portions of the plate body are formed before forming the water-repellant film, where the step of forming the water-repellant film forms the water-repellant film by immersing the plate body in the water-repellant film material and the protective tape is removed once the forming of the water-repellant film has been completed, after which the water-repellant film apertures are formed.
According to the nozzle plate of the present invention, by making the diameter of the jet aperture portion from which ink is jetted the same as the diameter of the water-repellant film aperture formed on the water-repellant film, the ink meniscus prior to jetting the ink maintains the same position. Specifically, the meniscus is formed at the interface between the plate body within the nozzle aperture and the water-repellant film.
By maintaining the meniscus at the same position in this manner it is no longer necessary to take into consideration the effect of fluctuations in the position of the meniscus when controlling the ink jet as in the conventional art, making it possible to easily control the ink jet. In addition, in this manner it is possible to achieve stable ink jetting and hence it is possible to perform high-quality printing.
By forming the water-repellant film of the present invention from resinous material the water-repellant film acquires excellent workability, making it possible to easily make the diameters of the water-repellant film aperture and the nozzle aperture the same.
According to the water-repellant film forming process of the nozzle plate manufacturing method of the present invention, by forming the water-repellant film on the plate body on which the nozzle aperture is formed and then forming the water-repellant film aperture and removing the water-repellant film remaining inside the nozzle aperture of which the surrounding area is masked by the plate body to form the water-repellant film aperture, the diameter of the water-repellant film aperture formed and the diameter of the jet aperture portion become the same.
In addition, in contrast to the conventional manufacturing method using a resist, with the nozzle plate manufacturing method of the present invention there is no need to control the resist processing conditions. As a result, it is possible to easily form a water-repellant film aperture of the same diameter as the jet aperture portion.
According to the nozzle plate manufacturing method of the present invention, by using either an excimer laser device, a carbon dioxide gas laser device, a carbon dioxide gas pulse laser device or a water jet device as the removing means the water-repellant film is removed by laser device light or by water jet, making it possible to easily and accurately remove the water-repellant film remaining inside the nozzle aperture compared to mechanical removal processes.
Particularly when using a carbon dioxide gas laser device as the removing means, the heat generated by the carbon dioxide gas pulse laser during operation causes the portion of the water-repellant film being worked to melt and to thereafter harden again, thus forming a smooth water-repellant film on the nozzle aperture and making it possible to improve the ink flow.
In addition, by performing a step of applying protective tape to a surface opposite the surface on which the jet aperture portion of the plate body is formed before forming the water-repellant film the entire nozzle aperture except for the jet aperture portion is sealed.
With the nozzle aperture except for the jet aperture portion in this sealed condition the plate body is immersed in water-repellant film material to form the water-repellant film. At this point, excess water-repellant film material is prevented from getting inside the nozzle aperture because the nozzle aperture except for the jet aperture portion is sealed with protective tape. By preventing excess water-repellant film material from getting inside the nozzle aperture the amount of excess water-repellant film material that intrudes into the interior of the nozzle aperture can be reduced, making it possible to form the water-repellant film aperture more easily and more efficiently.